Of the various types of superabrasive grinding wheels, e.g., pencil edging wheels, used to finish and make a sheet of glass ready for mounting by grinding a desired profile on the edge of the sheet of glass, to give it the desired shape and profile, e.g., for mounting into a motor vehicle it is necessary to grind a profiled edge on the outer periphery of the glass to give it the desired cross-section or edge profile to engage with the opening and/or for safety. Generally, this is done by a grinding machine that includes a diamond grinding wheel for providing the desired contour having a profiled abrasive portion. By way of example, a form edge on the outer periphery of the glass can be done by a pencil edging grinding machine, which includes a pencil edging wheel for providing the final contour on the sheet of glass. Such known types of pencil edging wheels have an abrasive portion with a U-shaped cross section to put a full radius on the edge of the workpiece, e.g., on the upper edge of a retractable glass window of a vehicle to engage with the weatherstripping.
Generally, conventional diamond abrasive grinding wheels are expensive to manufacture and manufacturing results in a large amount of scrap. Manufacturing conventional diamond abrasive wheels begins with processing of a blank of metal and it is common for metal blanks weighing about 20 pounds to be used in the manufacturing of a single wheel. Typically, during the process of forming a conventional wheel, a large blank of steel of about 20 pounds is processed and machined until the final wheel weighs about 6 pounds with the profiled abrasive portion having been formed therein, e.g., the U-shaped profile of a diamond abrasive pencil edging profile is formed therein. Processing the diamond abrasive layer of conventional wheels results in extensive waste, e.g., loss of 25% of diamond matrix which is wasted, as well as increased labor costs and equipment costs since the abrasive portion profile, e.g., the U-shaped profile, must be formed in a secondary operation, e.g., grinding out the profile after sintering, forming during cold pressing, and/or heating of the abrasive layer in a mold with the core. Additionally, an extensive amount of manufacturing processing steps and energy is employed to turn the large expensive blank of steel into a single pencil edging wheel with a profile having an abrasive grit matrix for grinding. These extensive, largely manual, laborious manufacturing steps and material costs, as well as in-bound shipping and material handling demands, causes the cost of conventional wheels to be much higher than desirable. They also reduce disposability of conventional wheels owing to their higher replacement costs. Accordingly, there is a great and long felt need in the industry for a method of making a diamond abrasive grinding wheel that reduces the amount of material used and extensive steps required to make it.
Conventional diamond abrasive grinding wheels are expensive to procure initially due to wheel manufacturing and material costs and also expensive to maintain over time. Generally, the abrasive portion is formed of diamond grit bearing matrix or other expensive abrasive material(s) matrix. Over time the abrasive portion profile can become worn, which results in decreased accuracy and/or causing the need for re-profiling of the wheel. For example, over time the radius or U-shaped profile of the grinding portion of conventional pencil edging wheels can become flattened or otherwise undesirably worn down distorting the desired shape and profile of the workpiece. Since conventional grinding wheels are typically not disposable, owing to their high replacement costs, the oversized diamond section abrasive portions are often re-trued or re-profiled multiple times, rather than the entire wheel being replaced every time the profile becomes worn. Typically, worn conventional wheels are shipped back to the manufacturer or a supplier where they are re-trued and shipped back to the user, which is known to be costly and time consuming. It also results in decreased productivity and downtime until a worn wheel is re-trued and returned and/or requires the user to have back-up wheels in stock so that manufacturing downtime is reduced.
Additionally, abrasive portions of conventional grinding wheels are generally non-segmented. A common problem with these wheels is that the non-segmented abrasive portions are less precisely located on the metal core and have a weaker metallurgical bond to the steel core and less consistency of the diamond grinding section. Such imprecision, weakness and decreased diamond section consistency can result in less precise grinding and can cause the grinding surface to become worn more quickly, which again, reduces productivity and increases costs. Additionally, the use of non-metallic matrixes, e.g., a powdered non-metal bonding matrix, ceramic powders, vitrified segments, and the like, for the abrasive portion and/or any non-metallic backing layer of the abrasive portion mounted to the core of conventional wheels is known to not provide an adequate bond, is less hard, and results in premature wear of the grinding wheel.
Another common problem with conventional diamond abrasive grinding wheels is that the metal core, which is typically of expensive steel, cannot be re-used with replacement abrasive portions. Because of the high processing temperatures and pressures used in the processing of the diamond abrasive grinding wheel, the steel core made from a large blank is machined substantially oversized to allow for deformation and distortion in the sintering and/or hot pressing of the wheel. Once the abrasive portion is damaged or worn beyond use it cannot be replaced on the original metal core.
There are some known grinding wheels with segment abrasive sections or layers bonded to a polymer section or core. These wheels commonly have the aforementioned problems. Additionally, these sections or layers of conventional wheels are also bonded to one another using cast or other bonding methods, in addition to bonding to any backing layer, which requires more material and processing steps to form and dress the abrasive sections or layers and bond them to the core resulting in increased costs. It also reduces or eliminates replaceability of individual abrasive sections or layers.
There are also other known methods for profiling the abrasive layer, e.g., forming a U-shaped groove profile for grinding, however, these are known to create imprecise profiles and weaker bonds. One such conventional known method uses a stint or form in the abrasive layer adjacent the wheel core while in the mold during heating, which does not allow uniform pressure across the diamond section during cold and hot pressing and tight dimensional tolerances of the profile and creates a weaker bond. Thus, additional grinding or comparable processing of the profile to achieve the desired shape and dimensions is necessary. In addition, a conventional continuous sintered metal bond diamond section is less consistent than desired.
Accordingly, there exists a need to provide a segmented profiled wheel of the type used for shaping and contouring of glass and/or non-metallic material workpieces that improves the grinding performance and longevity of the segmented profiled wheel and an improved cost effective and efficient method for making same.